Typically, in the manufacture of semiconductor devices or the like, a shower head has been used to supply a gas toward a substrate such as a semiconductor wafer or the like in a form of shower. For example, in a plasma processing apparatus for performing a plasma etching process on a substrate such as a semiconductor wafer or the like, a mounting table for mounting the substrate thereon is provided inside a processing chamber and a shower head is provided to face the mounting table. In the shower head, a plurality of gas injection holes is formed on a facing surface that faces the mounting table and a gas is injected toward the substrate through the gas injection holes in a form of shower.
In the plasma processing apparatus, a plasma generated in the processing chamber needs to be confined in a defined processing space. Accordingly, there has been disclosed a plasma processing apparatus in which the processing space of a processing chamber is provided with a plasma-confining baffle plate (see, e.g., Japanese Patent Application Publication No. 2004-165460 and corresponding U.S. Application Publication No. 2004-0149216 A1).
The above-described plasma etching apparatus is typically configured to exhausts the processing chamber through a lower portion thereof, so that a gas supplied from the shower head flows toward a lower side of the mounting table. For that reason, the plasma generated in the processing chamber tends to diffuse, according to the gas flow, around the mounting table and from around the mounting table toward a lower portion thereof. The conventional plasma-confining technique is to prevent such plasma diffusion.
In the meantime, the present inventors have been developing a shower head serving as not only a gas supply unit through which a gas can be supplied but also a gas exhaust unit having a plurality of gas exhaust holes through which gas exhaust is performed, to thereby improve the uniformity of gas flow. In the processing chamber, the gas flows from an upper side to a lower side in the space having such a shower head between the mounting table and the shower head and also from the lower side to the upper side. As a result, such gas flow is completely different from that in the conventional plasma processing apparatus. Accordingly, the above-described conventional confining method may not be employed in the apparatus equipped with such a shower head.
Therefore, it is required to develop a technique capable of preventing plasma dispersion for a shower head having exhaust holes through which gas exhaust is upwardly performed and a plasma processing apparatus having same.